Techniques have been known for bonding together a plurality of semiconductor substrates or semiconductor layers having semiconductor devices formed therein, as disclosed, e.g., in the following patent publications.
Japanese Laid-Open Patent Publication No. H01-133341 describes a technique of bonding an epitaxial Si layer or GaAs layer through an insulating film to an Si substrate, with these layers and the substrate having active elements formed therein. Japanese Laid-Open Patent Publication No. 2005-136187 describes a technique of bonding a GaAs layer to circuits on an Si substrate through projecting electrodes such as solder balls.
Japanese Laid-Open Patent Publication No. S63-205918 describes a technique of bonding an epitaxial AlGaAs layer through a low melting point metal layer to an Si substrate with an LSI formed therein. Further, Japanese Laid-Open Patent Publication No. H08-236695 describes a technique of bonding an AlGaAs layer through insulating layers to an Si substrate by Van der Waal's forces, wherein the AlGaAs layer has devices formed therein and the Si substrate has functional devices formed therein.
Compound semiconductor material can be used to manufacture semiconductor devices having superior characteristics, since it has better properties than other semiconductor material. However, the use of compound semiconductor material results in a considerably higher cost, since it is costly to form compound semiconductor layers and provide a semiconductor substrate of compound semiconductor material.
In semiconductor devices (e.g., high frequency semiconductor devices such as MMICs), semiconductor active elements, passive circuits, wiring conductors, and pads, etc. are formed on a semiconductor substrate to achieve the desired circuit configuration. It should be noted that passive circuits (including passive elements such as MIM capacitors and inductors) occupy more space than semiconductor active elements such as transistors and diodes. Therefore, if the design of a semiconductor device requires that all circuit elements (i.e., active elements and passive circuits) be formed side by side on the same compound semiconductor substrate, much of the available area on the compound semiconductor substrate (which is expensive) is occupied by the passive circuits. The result of this is that only a limited number of semiconductor devices can be manufactured from a single compound semiconductor substrate, making it difficult to reduce the chip manufacturing cost.